Engine noise, road noise, and aerodynamic noise are the primary sources of noise caused by a vehicle. As current efforts continue to decrease the engine and road noise, the relative contribution to noise from aerodynamic noise is increasing. Therefore, the aerodynamic noise must be reduced in order to reduce the overall amount of noise experienced in the vehicle or outside of the vehicle.
In order to determine the causes of aerodynamic noise from the vehicle, the aerodynamic noise from various point sources on the vehicle must be measured. A conventional method for measuring the aerodynamic noise uses an array of microphones stationed inside or outside the airstream at a fixed distance from the vehicle. However, limits on microphone size and geometry, as well as processing time, limit the effectiveness of this method. The microphone array also generates its own noise, which interferes with the measurement of the aerodynamic noise.